One important piece of context needs to be mentioned on Harold Bloom's list. It was not Bloom writing a list of the greatest works of all time. The list was a much narrower list of works: the works of American Literature from the 20th century that Bloom thought would still be read in the future. It was his list of future classics. This, then, explains the fact that all the authors on the list are 20th Century American writers--- otherwise it is close to inconceivable that even the worst literary snob would include three novels by Denis Johnson on a list that excluded James Joyce, Voltaire or Mark Twain.
But we are still left with a problem. An even bigger problem, in fact. Because the original subtitle was indeed part of the article: these are books that you should have read by now. Whether that was Bloom's contention, or just a provocative title tacked on by an editor at Esquire, this list seems to suggest that whoever is reading the list already has read every book on it, and if they haven't, there must be something wrong with them. The current reader of this piece, having read over the list, is probably thinking that the claim that these books should have been read already is somewhere between pretentious and ludicrous. But I will describe just how ludicrous it is.
How long does it take to read a book? I have actually read at least one of the books on the list (The Great Gatsby) inside of 24 hours, but that was a brief book. It is true that the actual speed of reading can be done quite quickly, and that reading a 500 page book in a day is not out of the question. However, properly reading and understanding a book usually is not done at a breakneck speed. Just like eating a good meal, you want to chew and digest it slowly. The rate at which these books could be read varies greatly, The Catcher in the Rye being a book that probably could be read in a day or two, while Gravity's Rainbow might take a much longer time. I would say that reading two of these books a week is not an impossible goal. At that rate, it would take a little over two years to have read all these books. Since these are books that involve a high reading level and mature concepts, reading them would probably begin (theoretically) around 16 to 18. Thus, it could be realistic to think that someone entering into college, or half way through it, could have read these books already.
Of course, these books, are, as mentioned, only taken from a particular niche of literature. The person who takes the task upon themselves of reading two of these books a week for three years would also have to forgo reading earlier American literature. And other English language literature. And foreign language in translation. And any sort of scientific, historical, philosophical, religious or technical literature. And, for that matter, any light reading. So our theoretical prodigy has given up on reading The Rise and Fall of the Third Reich, or War and Peace, or Wonderful Life, or Jurassic Park, and many other important books, so they can plow through Bloom's work of essential 20th century American literature. Either that or they would intersperse this reading amongst their other reading. But that brings our time line up from a rather optimistic two and a half year by a factor of several times. If we take a generous estimate that 20th century American literature would be one quarter of someone's diet, we are now up to ten years before these books "should" have been read. So again, our literary prodigy might be able to make this list by their late 20s, if we include several generous estimates in our calculations.
Of course, most people, even intelligent people, have other things to do with their lives, such as studying non-literary subjects in college, having a job or a family, or having hobbies or activities other than reading. So if ten years is the time frame it would take a dedicated literary enthusiast to get through these books, it might take several times that for someone who has other things to do. So our ten years might stretch out to twenty or thirty years for the average educated person. We are getting further and further away from "should have read by now". Under some bizarre set of literary obsession, this list of books might be something that has been read already, but even amongst people studying American literature in graduate school, there is probably one person in a hundred that has read every book on this list, or even a majority of them.
If this long deconstruction of the actual plausibility of this particular list seems unnecessary, I do it because I am making a larger point about the "canon". I would say the same thing about books such as "1001 Books To Read Before You Die". I consider, for both conceptual and logistical reasons, the canon of literature to be a starting place, instead of an exhaustive body of work. Conceptually, culture is quite large and there is no way to throw a net over it. Even if we have a "snobbish" view that there is a high culture of literature and philosophy that excludes science and popular works, the idea that you can cover every aspect of culture takes away from many of the intricacies of various disciplines within that culture. And from a logistical standpoint...well, I have already explained that. The purpose of a canon is to have a small body of work that the average educated person can have read, so that they have a common yardstick to compare their other fields of endeavor and interest to. And, for obvious reasons, having read several hundred books of modern American literature and poetry is not needed to do that.